They dont' need a book.
which is why Churchs don't update it. They are only going to sell books to new travellers and I'd say there aren't so many of them nowadays. In the case of Baja, maybe you don't even need a map to find a safe haven for the night.
When we were on the mainland a couple of years ago someone, maybe BrianSue, said Churchs were in Mexico getting updated info. Did anything come of that or did they decide then there was no money to be made so didn't follow through.
One thing that book was useful for was to navigate through cities and avoid places where bigrigs shouldn't be, but now everyone has fantastic databases and maps and navigation in the palm of their hand, plus on-line lists of millions of points of interest and the ability to pre-drive routes on your computer so the demand for this sort of publication is fast approaching zero.